Contact: Mark Church, Assessor-County Clerk-RecorderAlternate: Theresa Rabe, Deputy Assessor-County Clerk-Recorder Redwood City, CA – There were 5,478 new babies born in San Mateo County in 2010 and slightly more of them were boys (51.6 percent boys/49.4 percent-girls).  Last year, Isabella was the most popular name for girls and Ethan was the most popular name for boys.